The present invention relates to unexpected rubber-metal adhesion improvement for metal substrates which were prepared using ion beam etching and deposition.
Heretofore, wire used as reinforcement in rubber articles has been manufactured by coating the wire with a non-ferrous metal using conventional electroplating techniques. The coating material can consist, for example, of a layer of a brass alloy which is often used for the purpose mentioned. The specific composition and thickness of the coating material of the wire are restricted by manufacturing considerations. For example, a brass alloy coated on a reinforcing wire must contain at least 63 percent copper and be at least 1000 .ANG. thick.
It has been observed that moisture is generally very harmful for the adhesion between the steel reinforcement and the rubber article. For example, U.S. Pat. No. 3,749,558 notes that copper-plated steel wires display considerably higher adhesion failures after exposure to a 60 percent relative humidity environment than when exposed to a dry air environment. This has been of particular concern in recent years in which a strong demand is made of the safety and waterproofness of wire reinforced tires.
A number of methods have been described that prevent loss of rubber adhesion to conventionally prepared wires after moisture exposure. For example, U.S. Pat. No. 3,846,160 claims a process whereby the steel wire coated with brass alloy is immersed in a mineral oil solution prior to vulcanization. Another solution to the moisture problem calls for the use of a low copper content brass alloy as described in British Pat. No. 1,250,419. A third method to prevent adhesive degradation under corrosive conditions involves the use of ternary brass alloys containing copper, zinc, and cobalt as described in British Pat. Nos. 2,011,501A and 2,306,278. Finally, U.S. Pat. No. 3,749,558 describes the use of copper-nickel and copper-zinc-nickel alloy coatings on wire to prevent adhesion loss.
However, none of these patents relate to the use of ion beam deposition or etching or to improved rubber moisture age adhesion.
Ion beam sputter deposition and etching are relatively new techniques. For example, in an article "Adherence of Ion Beam Sputtered Deposited Metal Films on H-13 Steel" by Michael Mirtich, Lewis Research Center, prepared for the 27th National American Vacuum Society Symposium, Detroit, Mich., Oct. 14-17, 1980, it is noted that die life can be increased by sputter depositing molybdenum or chromium upon a casting die. Moreover, the tables set forth various other materials and the adherence thereof to a steel substrate.
In an article entitled "Advances in Low-Energy Ion Beam Technology," by W. Laznovsky, Research and Development, August 1975, pages 47-55, ion beams have been set forth as having been utilized for the etching of microcircuits, surface wave device contacts, and the like, in essence, whenever high resolution (in the submicrometer range) is required.
"Ion Beam Techniques for Thin and Thick Film Deposition," by C. Weissmantel, H. Erler, and G. Reisse, Surface Science 86 (1979), North-Holland Publishing Company, pages 207-210, relates to various techniques for sputtered depositing films of various metals or alloys.
An article entitled "Ion Beam Texturing" by Wayne Hudson of the NASA, Lewis Research Center, Cleveland, Ohio, published in the Journal of Vacuum Society Technology, in Volume 14, No. 1, January and February 1977, pages 286-287, relates to the use of texturing many surfaces such as stainless steel, titanium, aluminum, copper and silicon by ion beam sputtering in an attempt to provide a suitable optical coating.
In Optical Properties of Ion Beam Textured Materials by Hudson, Weigand, and Mirtich, Lewis Research Center, in a paper presented to the Sixth Annual Symposium on Applied Vacuum Science and Technology, Tampa, Fla., Feb. 14-16, 1977, ion beams are used to coat a solar apparatus.
In an article entitled "Ion Beam Sputtering of Fluoropolymers" by Sovey, NASA Lewis Research Center, Cleveland, Ohio, published in the Journal of Vacuum Science and Technology, March-April, 1979, the etching and deposition of fluoropolymers is described.
Finally, the article entitled "Characteristics of Ion-Beam-Sputtered Thin Films," by Kane and Ahn of IBM, published in the Journal of Vacuum Science and Technology, March-April, 1979, pages 171-172, relates to the thin films of various metals which have been prepared by ion beams sputtering with such films having excellent adhesion to a metal substrate.
Although the preceding representative articles describe ion beam sputtering or etching techniques, none relate to or even teach or suggest that adhesion of rubber to copper or brass-coated metals, such as those used in tire cord construction, rubber hoses, and with regard to any wire reinforced rubber article, would be improved.